The Inter-Integrated Circuit (I2C) bus is a bus for performing serial communication between a plurality of electronic circuits. The I2C bus is used for accessing a memory, reading detection values from various sensors such as a temperature sensor, and monitoring and controlling operations of an electronic circuit, for example.
In the case where one of a plurality of electronic circuits connected to a serial bus such as the I2C bus is abnormally terminated, the other electronic circuits might become unable to perform communication via the serial bus. As a technique for restoring communication via a serial bus from such a state, there has been disclosed a technique of resetting an electronic circuit connected to a serial bus by using a reset signal line that is provided separately from the serial bus (see, for example, Japanese Laid-open Patent Publication No. 2002-63080). There is also a system that includes a hang-up detection circuit between an electronic circuit and a serial bus. This system disconnects the electronic circuit from the serial bus when the hang-up detection circuit detects a hang-up of the electronic circuit (see, for example, Japanese Laid-open Patent Publication No. 2010-55474).
There is also another system that includes a plurality of switches on a serial bus. This system is configured to, if communication via the serial bus is disabled, turn off all the switches and then turn on the switches sequentially in the order from upstream so as to identify the location of the failure (see, for example, Japanese National Publication of International Patent Application No. 2004-528627).
By the way, in a system in which a control device controls operations of an electronic circuit via a bus, a bus interface for the electronic circuit receives a control signal from the control device via the bus, and outputs a signal corresponding to the received control signal to the electronic circuit. In the case where the bus becomes unusable in such a system, the bus may be restored by resetting the bus interface for the electronic circuit.
However, when the bus interface for the electronic circuit is reset, the output signal from the bus interface to the electronic circuit is lost. Therefore, even if there is no failure in the electronic circuit, the electronic circuit becomes unable to continue the last operation. For example, when the bus interface is reset, the electronic circuit is also reset.